Why Are So Many Women Giving Birth to Big Babies?

People were blown away in early June after it was announced that a woman in Florida gave birth to a 13.5-pound baby. Just weeks later, a mom in South Carolina grabbed headlines for having a 14-pound baby. Not to be outdone, parents in Indiana announced that in May they had a 16-pound baby.

The average birth weight in the U.S. is around 7.5 pounds — and these babies are clearly well above average. What’s going on here?

There are likely a few factors at play, Christine Greves, MD, a board-certified ob/gyn at the Winnie Palmer Hospital for Women and Babies, tells Yahoo Beauty. She’s not surprised that this is happening at the same time that the U.S. is facing an obesity epidemic. “With the incidence of maternal obesity increasing, that can result in babies being bigger and bigger,” she says.

Michael Cackovic, MD, a maternal-fetal medicine physician at the Ohio State University Wexner Medical Center, agrees. “The increase in obesity rates is certainly leading to bigger babies,” he says. Gestational diabetes, i.e. high blood sugar levels during pregnancy, can also cause women to have larger-than-average babies, he adds. While doctors test women for gestational diabetes during pregnancy, some women don’t get screened or fall just short of the diagnostic numbers for gestational diabetes, but still struggle with higher-than-normal blood sugar levels, he explains.

A woman’s age also matters, Greves says — the older a mother is, the more likely she is to have a bigger baby. And, once a family starts to have bigger babies, it’s likely to continue, Cackovic says. Birth weight is often determined on a genetic level by the mother, he explains, and that can be passed down through the family. “Once you start having big babies, you’ll probably keep having big babies.”

There’s actually a medical term for big babies — fetal macrosomia — and diagnostically it applies to newborns that weigh more than 8 pounds, 13 ounces, Jessica Shepherd, MD, an assistant professor of clinical obstetrics and gynecology and Director of Minimally Invasive Gynecology at the University of Illinois College of Medicine at Chicago, tells Yahoo Beauty.

Women who are pregnant with babies with fetal macrosomia have a few health considerations to be aware of, Shepherd says. The babies are at risk of shoulder dystocia, a serious condition in which the baby’s head is delivered vaginally, but the shoulders get stuck. It can be life-threatening to the baby, Cackovic says, which is why doctors often recommend a C-section birth for women who have babies that are measuring more than 9.9 pounds. (However, the cut-off is lower for women with gestational diabetes.) A vaginal delivery for a baby with fetal macrosomia can also cause vaginal tearing for the mom. “It can be much more significant, harder to repair, and harder to recover from because the tears and lacerations are much more significant,” Shepherd says. As for the babies themselves, extra large newborns are at a greater risk of hypoglycemia, respiratory problems, and childhood obesity, Greves says.

Of course, it’s also possible to have a perfectly healthy baby with fetal macrosomia and no complications with a delivery — women who have larger babies are just at an increased risk.

Despite all of the headlines recently, Shepherd says she doesn’t expect that everyone is suddenly going to start having extra-large newborns. “Those babies are outliers,” she says. “But I do think that we are going to start seeing an increase in the incidence of big babies.”